How to setting nodes for making a shop sign (lighting)
Cycles works with shaders that describe the interaction with light.

BSDF shaders
Describe light reflection, refraction and absorption at an object surface.

For more info read: What is a BSDF? and https://docs.blender.org/manual/en/dev/render/cycles/materials/surface.html#bsdf-parameters

A Diffuse BSDF shader does not emit light.

You need a shader that does! So use an

Emission shader

Used to describe light emission at an object surface or in a volume.



More info: https://docs.blender.org/manual/en/dev/render/cycles/nodes/introduction.html?highlight=shader